Process for the manufacture of net-like structures from synthetic fibers



July 3, 1962 K. RYFFEL 3,

PROCESS FOR THE. MANUFACTURE OF NET-LIKE STRUCTURES FROM SYNTHETIC FIBERS Filed June 4, 1958 5 mlllllllll INVENTOR.

KASPAR RYFFEL MESTERN 8 MEST'ERN United States Patent PRGCESS FOR THE MANUFACTURE OF NET-LIKE Synthetic fibers, particularly those of polyesters, polyacrylonitrile, polyvinylchloride and polyamides, usually have a circular diameter and a smooth surface. They thereby ditfer principally from natural fibers such as wool, cotton and silk, which have a rough, scaly surface structure.

Synthetic fibers of a diameter of 0.05 mm. often are referred to as wires and are as such particularly suited for the manufacture of fish nets and other net-like structures on account of their high tear-resistance and practically unlimited fungus resistance.

However, the smooth surface of synthetic fibers and the therewith connected small specific surface is disadvantageous for the production of net-like structures. Furthermore, wires having a diameter of approximately 0.5 mm. or more are difiicult to knit because of their rigidity.

It has been suggested to alter the surface of synthetic fibers chemically, mechanically or by application of a surface preparation (U.S. Patent 2,823,576). However, it has been found that, aside from the difliculties of treating the wires, these processes inflict damage to the material and that the rigidity thereby is not overcome.

According to Italian Patent 571,338, knitted structures can be manufactured from polycaprolactam wires which are quenched in oily liquids immediately after leaving the spinning jet. The slide resistance of the loops is effected by a heat treatment under tension.

It has now been found that net-like structures having knots resistant to sliding can be manufactured from synthetic fibers of non-circular cross-section, particularly of angular cross-section.

The production of synthetic fibers having a non-circular cross-section, e.g. a ribbon or star-shaped diameter, as such is known. Such fibers presumably impart to the textile products made therefrom a soft touch and also increased bulk or covering power.

The object of the present invention, therefore, is not a method for the preparation of fibers having a non-circular cross-section, but it is a manufacture of net like, knotted structures from non-circular synthetic fibers. It has been found that among wires having non-circular cross-sections those having a triangular shape are particularly suited for the manufacture of net-like structures having knots resistant to sliding. The employment of ribbon-shaped synthetic wire leads to results not quite as good with regard to the slide resistance and to the tightness of the knots.

In general, it is not necessary to fix the knots by means of a special heat treatment when non-circular synthetic fibers are used. This is particularly true when the synthetic fibers are extruded from polycaprolactam melts,

containing low molecular constituents, through suitably shaped spinning jets into oily liquids. As oily liquids, high-boiling fractions of the petroleum distillation having low volatility may be used, e.g., parafiin oil.

When thick wires are knotted into nets, i.e. wires Whose circular diameter superimposed on their actual crosssection is more than 1 mm., it is advantageous to improve the slide-resistance of the knots by a heat treatment. Such fixing treatment of the knots is executed best by pulling the net-like structure under tension through a heated bath of a liquid which is not a solvent for the synthetic fiber. It is also possible to fix the knots by pulling ice the net, preferably also under tension, along a heated surface.

Nets made according to the present invention are highly suited for use as fish nets.

The accompanying drawing illustrates several profiles and a flowsheet of the heat-setting step.

In the drawing,

FIG. 1 is a monofilament of triangular cross section which may be used for producing a net according to the instant invention.

FIG. 2 is a monofilament of rectangular cross section which can be used for the same purpose.

FIG. 3 shows a knot tied from a triangular thread.

FIG. 4 shows the same knot in loosened condition indicatin g the strands with greater clarity.

FIG. 5 is a diagrammatical side view of a heat-setting device.

FIG. 6 shows a diagrammatical view of a net.

In FIGURE 5, the points 3 and 4 show the knots as illustrated in FIGS. 3 and 4, respectively.

Referring to FIG. 6, the net 4, corresponding to FIG. 4, enters the device over rollers 5, 6 and 7, revolving at the same speed; 8, 9 and 10 are rollers, also rotating at the same speed but faster than rollers 5, 6 and 7. The envelopes 11 contain the heating elements 12.

The present invention will now be further illustrated by means of the following examples. However, it should be understood that these are given merely by way of explanation, not of limitation and that many changes may be made in the details without departing from the spirit of the present invention.

Example 1 A net is made in a known manner from a polycaprolactam fiber whose cross-section of 0.052 rnm. has; the shape of an equilateral triangle. The net is spread in such a manner that the knots are exposed for 5 minutes to a tension of 1 kg. The tightness of the knot thereafter is 2.8 kg., the resistance to sliding is 0.81 kg. If the net during stretching is simultaneously subjected to a heat treatment so that the knots are exposed to a temperature of C. for 5 minutes under tension, the slide resistance is 1.65 kg.

If the cross-section of the polycaprolactam Wire is rectangular instead of triangular, i.e. if the wire is a ribbon of the dimensions 0.5 x 0.1 mm., the tightness of the unfixed knot is 2.8 kg, whereas the slide resistance of the unfixed knot is 0.64 kg. and that of the fixed knot is 1.08 kg.

The corresponding values for a circular polycaprolactam fiber of approximately the same cross-section, i.e. a diameter of 0.25 mm. are as follows:

The tightness of the knot is 1.79 kg. The slide resistance of the unfixed knot is 0.48 kg. The slide resistance for the fixed knot is 0.75 kg.

Example 2 The method is the same as described in Example 1 except that polycaprolactam fibers having a cross-section of 0.126 mm. are used. In nets made from triangular wires, the tightness of the knot is 4.5 kg, the slide resistance of the unfixed knot after stretching for 5 minutes at a tension of 2.5 kg. per knot at room temperature is 1.30 kg.

If ribbons of a cross-section of 0.6 x 0.2 mm. are used, the corresponding values are 3.9 kg. for the tightness of the knots, 1.07 kg. for the slide resistance of the unfixed knots and 1.83 kg. for the slide resistance of the fixed knots. If a circular wire of approximately the same cross-section is used, i.e., of a diameter of 0.43 mm., the tightness of the knot is 3.2 kg, the slide resistance of the unfixed knot is 0.80 kg, that of the fixed knot :is 1.34 kg.

What I claim is:

l. A process for the manufacture of net-like structures 3 having tight and slide-resistant knots, made of polycaprolactarrrfibers-containing low-molecularconstituents and having angular cross section, which comprises extruding said po lyoaprolactam into fibers and quenching them into an oily 1iquid,*=knotting the fibers into a net,-andtsubjecting the net to a tension of approximately 1 kg. for approximate1y5minutes.

12. A process for the manufacture of'net-iike structures having tight ands1ide-resistantknots, made of polycaprolactam fibers containing-low-moiecular constituents and having angular cross section, which comprises extruding said polycaproiactam i-nto fibers and quenching them into an oi1y=iiquidgknotting the fibers intoa; net, and subjecting the net to a tension of approximately 1kg. for approximately 5 minutesat approximately 130 C.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A PROCESS FOR THE MANUFACTURE OF NET-LIKE STRUCTURES HAVING TIGHT AND SLIDE-RESISTANT KNOTS, MADE OF POLYCAPROLACTAM FIBERS CONTAINING LOW-MOLECULAR CONSTITUENTS AND HAVING ANGULAR CROSS SECTION, WHICH COMPRISES EXTRUDING SAID POLYCAPROLACTAM INTO FIBERS AND QUENCHING THEM INTO AN OILY LIQUID, KNOTTING THE FIBERS INTO A NET, AND SUBJECTING THE NET TO A TENSION OF APPROXIMATELY 1 KG. FOR APPROXIMATELY 5 MINUTES. 